(1) The field of the invention comprises a process for producing gamma butyrolactones from olefins, in the presence of a reducible metal ion, described below, wherein such metal ion is reduced, and wherein the reduced metal ion is regenerated to higher valent form and recycled. (2) In the environment described, the invention provides for a significant economy in the ability to reuse the reducible metal or compound thereof. Convenient handling of the reduced metal or compound thereof is possible by taking care to employ it in a pumpable form, i.e., as a solution or a pumpable slurry. Following regeneration, the effluent thereof may be used directly by recycling the same to the reaction zone. Time-consuming operations like filtration are avoided. It is believed that the described process is new.